9
DMAC
9-21
32180 Group User’s Manual (Rev.1.0)
9.2.5 DMA Transfer Count Registers
DMA0 Transfer Count Register (DM0TCT)
<Address:
H
’0080 0416>DMA1 Transfer Count Register (DM1TCT)
<Address:
H
’0080 0426>DMA2 Transfer Count Register (DM2TCT)
<Address:
H
’0080 0436>DMA3 Transfer Count Register (DM3TCT)
<Address:
H
’0080 0446>DMA4 Transfer Count Register (DM4TCT)
<Address:
H
’0080 0456>DMA5 Transfer Count Register (DM5TCT)
<Address: H
’0080 041E>DMA6 Transfer Count Register (DM6TCT)
<Address: H
’0080 042E>DMA7 Transfer Count Register (DM7TCT)
<Address: H
’0080 043E>DMA8 Transfer Count Register (DM8TCT)
<Address: H
’0080 044E>DMA9 Transfer Count Register (DM9TCT)
<Address: H
’0080 045E>b0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 b15
DM0TCT–DM15TCT
????????????????
<After reset: Undefined>
b Bit Name Function R W
0–15 DM0TCT–DM9TCT DMA transfer count R W
(Has no effect during ring buffer mode)
Note: • This register must always be accessed in halfwords.
The DMA Transfer Count Register is used to set the number of times data is transferred on each channel.
However, the value in this register has no effect during ring buffer mode.
The transfer count is the (value set in the transfer count register + 1). Because the DMA Transfer Count Register
is comprised of a current register, the values read from this register are always the current value. (However, if
the register is read in a cycle immediately after transfer, the value obtained is one that was stored in the count
register before the transfer began.) When transfer finishes, this count register underflows and the value read
from it is H’FFFF.
When transfer is enabled, this register is protected in hardware and cannot be accessed for write.
During ring buffer mode, the transfer count register counts down in free-run mode and continues counting until
transfer is disabled. No interrupt is generated at underflow.
If any cascaded channel exists, each time one DMA transfer (byte or halfword) is completed or when all trans-
fers on a channel are completed (i.e., the transfer count register underflows), transfer on the cascaded channel
starts.
The DMA Transfer Count Register must always be accessed in halfwords (16 bits) beginning with an even
address. If accessed in bytes, the value in this register is undefined.
9.2 DMAC Related Registers
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